1. Field of the Invention
The present invention relates to an ink set for ink-jet recording, comprising a yellow ink containing a yellow coloring agent, water and a water soluble organic solvent; a magenta ink containing a magenta coloring agent, water and a water soluble organic solvent; and a cyan ink containing a cyan coloring agent, water and a water soluble organic solvent.
2. Description of the Related Art
Generally, inks employed for forming an ink-jet recorded image are required to satisfy the following ink-jet recording properties to a high degree:
(1) To provide a vivid image having excellent color developing properties.
(2) To provide excellent toughnesses properties such as light fastness, active gas (oxidizing gases such as NOx and ozone, SOx and the like) resistance, water resistance, and the like.
(3) To exhibit no problem when the inks contact various members employed in an ink-jet recording apparatus.
(4) To provide excellent storage stability, and stability of use over long time with minimal chance of clogging the nozzles of an ink head, thereby maintaining satisfactory ejection stability.
In particular, when a natural image or the like is represented by subtractive color mixing of yellow, magenta and cyan, it is highly required that the hues of yellow, magenta and cyan inks be close to the hues of standard yellow, standard magenta and standard cyan, respectively, and that each of the inks provides vivid color. It is required that a printed natural image and the like have excellent long-term storage stability such that excellent color developing properties and high optical densities can be maintained. Therefore, it is important that the inks not only have excellent light fastness and active gas resistance but also exhibit excellent hue balance. In particular, it is important that color fading properties of the yellow, magenta and cyan inks be well balanced. Hence, an ink set for ink-jet recording has been proposed in view of the above requirements (see U.S. Pat. No. 6,488,751).
However, in conventional technologies, an ink-jet recording ink of any of the yellow, magenta and cyan colors has a problem in that the toughnesses properties such as light fastness and active gas resistance are insufficient. Therefore, deterioration of the ink-jet recorded material may occur as a result of use of these conventional ink-jet recording inks.
It has been generally known that, among magenta dyes employed for ink-jet recording, a magenta dye providing vivid color and having a hue suitable for obtaining a wide range of colors by color mixing has a low level of light fastness and active gas resistance. Conversely, a magenta dye with excellent light fastness and active gas resistance has a hue insufficient to obtain a wide range of colors by color mixing and also has insufficient vividness. In addition to this, such a magenta dye is likely to cause problems when it contacts various members employed in an ink-jet recording apparatus, causing an impediment to long-term stable use of the ink-jet recording apparatus.
Generally, a phthalocyanine-based cyan dye employed for ink-jet recording is characterized by having light fastness superior to that of the magenta and yellow dyes but is likely to cause problems due to the solubility of the dye. For example, incomplete dissolution often occurs during manufacture of the cyan ink, causing manufacturing problems. Furthermore, insoluble materials often precipitate during storage or use of the cyan ink product, causing various problems. In particular, in the ink-jet recording described above, clogging of nozzles of an ink-jet head or ejection failure occurring due to precipitation of dye causes significant deterioration of the printed image or other problems. Furthermore, color fading due to active gases such as ozone is likely to occur, and thus a serious problem exists in that printing density is significantly decreased.